覆晶式氮化鎵發光二極體之低溫共晶接合研究

Abstract

現今，LED固態照明已越來越普遍，因此高功率的LED已越來越 重要。而LED輸出的效率中大約有30%轉換成光的形式輸出，而70%會以熱的形式輸出。因此散熱的議題已日趨重要。在此研究中，我們使用了氮化鎵覆晶式發光二極體(flip-chips)的方式，並且使用低溫共晶接合技術，希望能有效改善散熱的議題。 第一部分的研究為低溫共晶接合製程，我們所使用的接合材料為Sn0.7Cu，此材料的熔點為227℃,比起LED常用的接合材料An20Sn熔點279℃低，並且價格也較低。但是此材料在二段封裝時遇到了一大困難點，就是在二段封裝時，會發生重熔的問題，而此問題會使得熱阻嚴重上升，進一步會使得元件壽命變差。 所以第一部分的低溫共晶接合技術的研究，最主要是在改善重熔的問題，以優化此技術。 第二部分中，我們藉由第一部分的技術改良後，將改良前和改良後的結果去量測熱阻值，以計算出這兩種不同的晶片到共晶段的溫度。而此結果的差異對於接下來的的EL頻譜、CIE色座標偏移量、可靠度測試等..量測結果都有一定的影響，綜合所有的量測結果，對於光性和散熱特性，可得出改善後的結果已大大優化了改善前的結果。因此在我們研究中，完成了低溫共晶接合製程和低價格的技術。

Nowadays, LED solid-state lighting has become widely, therefore high- power LED has become increasingly important. The output efficiency of LED is transferred to optical type about 30%; heat type about 70%.So the heat dissapation is more and more important. In my study, we use the flip-chip LED based on GaN material. And we try to use low temperature eutectic bonding technology to improve the heat dissipation issue effectively. The first part we investigate the low temperature eutectic bonding, we use Sn0.7Cu solder, which melting point is 227℃, Its lower than An20Sn(melting point is 279℃) which we often used. And the price of Sn0.7Cu is lower than An20Sn.But this material has a big difficulty at second package. It is “re-melting”. This issue cause the thermal resistance increased.Further it can decay the LED device life time. So we solve the re-melting issue mainly in my first part to optimize this technology The second part , we will measure the thermal resistance for re-melting result and improve result. Them we can calculate the LED temperature from junction to die attach region for these two condition. And the result between re-melting and improve result is strongly affect EL spectrum 、relative output power、CIE offset、reliability and so on. Integration all measure result, the improve result optimization greatly for optical and heat characteristic. So in my study ,we have already developed a low temperature and low price technology.